Re: Using replaceInPlace, string and char[]
Must create a ticket for it ? I think so. Unless others object in 10 minutes... :) :-) Done : https://issues.dlang.org/show_bug.cgi?id=14925 Thanks for your help
Using replaceInPlace, string and char[]
Hi,
A newbie question :
I wrote this simple code :
import std.array;
import std.stdio;
void main()
{
char[] a = mon texte 1.dup;
char[] b = abc.dup;
size_t x = 4;
size_t y = 9;
replaceInPlace( a, x , y, b );
writeln( a );
}
But compilation fails :
/usr/include/dmd/phobos/std/array.d(2052): Error: template
std.algorithm.remove cannot deduce function from argument types
!()(char[], Tuple!(immutable(uint), uint)), candidates are:
/usr/include/dmd/phobos/std/algorithm.d(8542):
std.algorithm.remove(SwapStrategy s = SwapStrategy.stable, Range,
Offset...)(Range range, Offset offset) if (s !=
SwapStrategy.stable isBidirectionalRange!Range
hasLvalueElements!Range hasLength!Range Offset.length = 1)
/usr/include/dmd/phobos/std/algorithm.d(8623):
std.algorithm.remove(SwapStrategy s = SwapStrategy.stable, Range,
Offset...)(Range range, Offset offset) if (s ==
SwapStrategy.stable isBidirectionalRange!Range
hasLvalueElements!Range Offset.length = 1)
/usr/include/dmd/phobos/std/algorithm.d(8757):
std.algorithm.remove(alias pred, SwapStrategy s =
SwapStrategy.stable, Range)(Range range) if
(isBidirectionalRange!Range hasLvalueElements!Range)
inout.d(13): Error: template instance
std.array.replaceInPlace!(char, char[]) error instantiating
Don't understand why this doesn't work: it compiles fine and runs
perfectly if I change char[] by string ... don't understand
why since the documentation says :
String literals are immutable (read only).
How this function can change a type that is immutable ?
Thanks for your help.
TSalm
Re: Using replaceInPlace, string and char[]
On Saturday, 15 August 2015 at 08:07:43 UTC, Ali Çehreli wrote:
This looks like a bug to me. The template constraints of the
two overloads are pretty complicated. This case should match
only one of them.
Yes I understand. I've used ldc2. With DMD (v0.067.1) the error
is more clear :
inout.d(11): Error: std.array.replaceInPlace called with argument
types (char[], uint, uint, char[]) matches both:
/usr/include/dmd/phobos/std/array.d(2214):
std.array.replaceInPlace!(char, char[]).replaceInPlace(ref char[]
array, uint from, uint to, char[] stuff)
and:
/usr/include/dmd/phobos/std/array.d(2247):
std.array.replaceInPlace!(char, char[]).replaceInPlace(ref char[]
array, uint from, uint to, char[] stuff)
Must create a ticket for it ?
Don't understand why this doesn't work: it compiles fine and
runs
perfectly if I change char[] by string
You mean, this:
import std.array;
import std.stdio;
void main()
{
string a = mon texte 1;// -- now string
writeln(a.ptr); // added
char[] b = abc.dup;
size_t x = 4;
size_t y = 9;
replaceInPlace( a, x , y, b );
writeln( a );
writeln(a.ptr); // added
}
The output:
4BC480
mon abc 1
7FC2AB867210-- different
... don't understand why
since the documentation says :
String literals are immutable (read only).
How this function can change a type that is immutable ?
It cannot change the characters of the original string.
replaceInPlace takes its first parameter by reference. What
changes is 'a' itself. As evidenced by the output of the
program, 'a' is now a slice to a new set of immutable
characters.
If there were other slices to mon texte 1, they wouldn't see
a change.
Yes I understand, thanks. In the other hand using string is not
efficient since this certainly make a copy of the original
string. Right ?
This is better to use replaceInPlace with char[], but this
doesn't actually work :-(
Re: Using replaceInPlace, string and char[]
This looks like a bug to me. The template constraints of the two
overloads are pretty complicated. This case should match only one of them.
On 08/15/2015 12:43 AM, TSalm wrote:
Don't understand why this doesn't work: it compiles fine and runs
perfectly if I change char[] by string
You mean, this:
import std.array;
import std.stdio;
void main()
{
string a = mon texte 1;// -- now string
writeln(a.ptr); // added
char[] b = abc.dup;
size_t x = 4;
size_t y = 9;
replaceInPlace( a, x , y, b );
writeln( a );
writeln(a.ptr); // added
}
The output:
4BC480
mon abc 1
7FC2AB867210-- different
... don't understand why
since the documentation says :
String literals are immutable (read only).
How this function can change a type that is immutable ?
It cannot change the characters of the original string. replaceInPlace
takes its first parameter by reference. What changes is 'a' itself. As
evidenced by the output of the program, 'a' is now a slice to a new set
of immutable characters.
If there were other slices to mon texte 1, they wouldn't see a change.
Ali
Re: Using replaceInPlace, string and char[]
On 08/15/2015 01:47 AM, TSalm wrote: Must create a ticket for it ? I think so. Unless others object in 10 minutes... :) In the other hand using string is not efficient since this certainly make a copy of the original string. Right ? This is better to use replaceInPlace with char[], but this doesn't actually work :-( There is probably a workaround, which others will hopefully show. (I have to leave now. :) ) However, although not in your example, replaceInPlace would still copy if the result would not fit in the original char[]. Hm... Come to think of it, it cannot replace in place anyway, unless it knows that the slice is the only one looking at those characters. Otherwise, you would disturbing your other slices. (?) Ali
